Re-inforced lead wires



P 21, 1965 w. J. HARRISON 3,208,036

RE-INFORCED LEAD WIRES Filed Oct. 9, 1961 INVENTOR 24 William J.Harrison mg zm ATTORNEY-5 United States Patent 3,208,036 REINFORCED LEADWIRES William Joseph Harrison, Mount Carmel, 11]., assignor to AmericanMachine & Foundry Co., a corporation of New Jersey Filed Oct. 9, 1961,Ser. No. 143,820 2 Claims. (Cl. 339-275) This invention relates to are-inforced lead-out wire structure for fine wire electric coils and thelike such as in relay coils, transformers, wirebound resistances, etc.and to methods and apparatus for making the same.

One of the weakest points in the structure of an electrical coil isadjacent the terminals where the delicate lead-out wire is brought fromthe ends of the coil to some type of terminal connection. With the finesizes of wires utilized, this portion of the wire is particularlysusceptible to breakage during manufacture of the coil and subsequentinstallation thereof. Furthermore, during operation of a relay or likedevice in which the coil is installed, the unit is generally subjectedto a substantial amount of vibration, providing another possible causeof breakage.

The problem of re-inforcing the delicate lead-out wire has beenrecognized in the past and has been partially solved by one of severalstructures. For example, the lead-out wire can be wound about a heavysupporting wire for strength, or may be interlaced with a plurality ofsmaller wires to similarly provide a strengthened portion. In thesestructures, either the strengthening wires are uninsulated or else theend of the strengthening wire spaced from the terminal is bare andexposed. Additional insulation is therefore required, surrounding thelead-out structure to insulate the structure from the remaining portionof the coil. The requirement for this insulation adds expense, andcauses a lump in the finished coil which substantially reduces theavailable winding space. Another disadvantage of prior structures ofthis type is that they often result in a stress concentration spacedfrom the terminal point, therefore creating a new weak spot in thelead-out wire.

This invention provides a lead-out structure, and a method of making thesame, which avoids the problems encountered with lead-out wirearrangements re-inforced in accordance with prior art proposals. Thereinforced portion of the lead-out wire is so arranged that noadditional insulation is required and expense and space requirements aretherefore reduced. Furthermore, the lead-out structure of this inventionpermits ease of manufacturing, further reducing the cost of thisstructure.

The unique results in accordance with this invention are achieved byemploying an insulated reinforcing wire having an open loopconfiguration. This loop is interlaced with the lead-out wire in theform of a stable twisted structure. More specifically, the loop istwisted to form two identical helices side by side about the same centerdefining a continuous helical valley between adjacent convolutions. Thelead-out wire nests in the helical valley so defined. The resultingstructure has three loose ends, i.e., two ends from the loop and onefrom the leadout wire, with the bend of the loop spaced a substantialdistance therefrom. The lead-out wire emerges from the structure bypassing through the loop formed by the bend. This lead-out structure canthen be completed by fastening all of the ends to a terminal connectorby means of a single solder joint. A unique feature of this structure isthat the reinforcing wire is completely insulated at all points spacedfrom the terminal connection and therefore no additional insulation isrequired for the strengthening structure.

The unique method for forming this re-inforced leadout structureincludes the operational steps of first form- 32%,036 Patented Sept. 21,1965 ing an open elongated loop of insulated Wire, the loose endsthereof being spaced from the center line of the loop. Next, the finelead-out wire is positioned between adjacent sides of the loop somewhatoff center. Then, while maintaining the spatial relationship between thethree ends, i.e., the loose ends of the loop and one end of the lead-outwire, they are rotated relative to the bent portion of the loop. Theresulting structure of intertwined wires forms a stable twistedconfiguration acting as a reinforced leadout wire.

The apparatus for carrying out the method in accordance with thisinvention is relatively inexpensive and simple. The basic components area coil spring rotatable about its center and a stationary post member.The three ends are secured between adjacent coils of the spring with afriction grip, this grip supplying proper tension to the wires. The postmember is adapted to retain the bend of the loop stationary when thespring rotates.

In order that the manner in which these and other objects are attainedin accordance with the invention can be understood in detail, referenceis had to the accompanying drawings, which form a part of thisspecification, and wherein:

FIG. 1 is a perspective view showing the forming of an elongated loop ofinsulated reinforcing wire;

FIG. 1a is a sideview of a portion of the unit of FIG. 1;

FIG. 2 is a similar perspective view illustrating the positioning of alead-out wire with respect to the loop;

FIG. 3 is a perspective view showing the loop and lead-out wire afterbeing intertwined;

FIG. 4 is a perspective view illustrating the completed lead-outstructure;

FIG. 4a is an enlarged fragmentary perspective view of a portion of theleadout structure shown in FIG. 4'; and

FIG. 5 is a perspective view of the lead-out structure installed on acoil form preparatory to winding of the coil.

Suitable apparatus for constructing a re-inforoed leadout wire is shownin simplified form in FIGS. 1-3 and includes an electric motor 1positioned on a mounting block 13a secured to a base member 13. Themotor has a rotatable driven shaft 2. Securely fastened to shaft 2 is arigid U-shaped member or yoke 3 adapted to maintain a coil spring 4between the legs or extended portions 3a thereof. Member 3 is so mountedon shaft 2 by that of offset portion 2a that, when spring 4 extendsbetween the legs of member 3 in straight line fashion, as illustrated inFIGS. 1 and la, the spring is centered on the axis of rotation of theshaft. Spring 4 is so dimensioned that, with its ends attached to thelegs of member 3, the spring is substantially relaxed, so that itsadjacent convolutions are closely adjacent to each other.

A stud member or post 5 is mounted on base member 13 at a point spacedaxially a substantial distance from the end of shaft 2. Post 5 extendsin a line which is at right angles to, and intersects, the axis ofrotation of shaft 12. At its tip, the post has a portion 6 of reduceddiameter to receive the bend of elongated wire loop 7.

Loop 7 is formed of a suitable insulated wire. Normally, this wire is ofa somewhat larger diameter than the lead-out wire to be re-inforced andis preferably a multi-strand wire. The nature of the insulation on thewire of the loop depends mainly upon the contemplated use of the coilbeing constructed, the insulation being designed to withstand thepotential and temperatures contemplated for the coil. One of the moreadvantageous types of wire which may be employed for the loop 7 is amulti-strand wire containing, for example, two or three strandsapproximately the same size as the lead-out wire, this multi-strand wirebeing coated by a continuous film of polyethylene, nylon,polytetrafluoroethylene or like resinous material. This type ofmulti-strand wire has the advantage of providing a twisted irregularouter surface providing space within which the lead-out wire may nest.

The open elongated loop 7 is substantially V-shaped and has two adjacentsides 8 and 9. The rounded bend 10 of the loop is engaged about reducedtip portion 6 of stud 5, the free ends of the loop, i.e., ends 11 and12, being each secured in spring 4 by pressing the wire between adjacentcoils. Ends 11 and 12 are spaced at equal distances from the center ofthe spring, and thus from the axis of rotation of shaft 2.

Lead-out wire 14 is then placed over the center of the tip 6 of stud andsecured in spring 4, as shown in FIG. 2. Lead-out wire 14 is locatedbetween adjacent sides 8 and'9 but is secured in spring 4 at a pointsomewhat off center, and, as shown in FIG. 2, is fastened closer to end11 than to end 12. Lead-out wire 14 is usually a very small diameterwire and therefore cannot be forced into spring 4 as this would oftencause breakage of the wire. Therefore, a suitable means (not shown) suchas a lever or plunger arrangement is employed to bow out spring 4 intothe position shown in FIG. 2. In this position, adjacent coils of spring4 are separated somewhat on the upper surface of the spring (as viewed),this separation allowing the lead-out wire to be inserted betweenadjacent convolutions of the spring without danger of breakage. Spring 4is then permitted to return to its normal position, so that the adjacentconvolutions clamp the lead-out wire in a position aligned with ends 11and 12.

Once the loop and the lead-out wire are positioned as shown in FIG. 2,motor 1 is turned on and permitted to rotate for a predetermined numberof revolutions. Rotation of the motor rotates yoke 3 and spring 4 totwist the wires, this twisting resulting in a shortening of the distancebetween the ends 11, 12 and 15 and the bend 10. As this shortening takesplace, the ends slide through the spring, the friction grip of thespring maintaining the required tension on the wires. As shown in FIG.3, the length of ends 11, 12 and 15 is less after the twisting operationis completed.

FIG. 4a shows the resulting twisted configuration. The adjacent sides ofthe loop, being of the larger diameter stranded wire, form two identicalhelices 16 and 17 side by side about the same center. The helices 16 and17 define two separate identical helical valleys 18 and 19 betweenadjacent convolutions of helices 16 and 17. The fine lead-out wire 14nests in the helical valley 18. This twisted configuration ofintertwined or interlaced wires is relatively stable and does not tendto unravel and therefore lead-out wire 14 cannot easily come free.

Once the twisting operation is completed, the bend is removed from stud5 and the entire assembly merely pulled out of spring 4. The loose ends11, 12 and are shortened and then securely fastened to a terminal lug 21by means of a single solder joint 22, as shown in FIG. 4. v

The re-inforced lead portion 27 can then be positioned on a coil windingbobbin, as shown in FIG. 5. The bobbin on which the coil is to be formedincludes ends 24 and 25 and a spindle 26 connecting the ends. Thereinforced lead 27 is positioned adjacent end 25, reaching to thespindle 26. The re-inforced portion is maintained in position by a splitwasher 28 having a slot 29 which permits the washer to be slid intoposition around the bobbin spindle 26. Once the re-inforced lead-outwire is positioned and secured, the bobbin is rotated to wind a coilwith the fine wire 30 which connects to terminal lug 31 via re-inforcedlead portion 27. When the coil is completed, the other end of the coilis similarly re-inforced to provide the second strengthened lead-outwire.

While the most advantageous embodiment of the present invention has beenshown, the scope of the invention is by no means limited thereto. Thescope of the present invention is more specifically defined in theappended claims.

What is claimed is:

1. A re-inforced electrical coil lead comprising a coil lead wire ofsmall diameter and terminating in a free end; a re-inforcing strand ofsubstantially larger diameter than said coil lead wire and having twofree ends, the central portion of said re-inforcing strand extending inthe form of a small closed free loop and the portions of saidre-inforcing strand between said loop and the free ends of said strandbeing twisted together in the form of two side-by-side helices having acommon central axis, said helices defining a continuous helical valley,said coil lead wire extending from its free end along said continuoushelical valley and being nested therein, said coil lead wire emergingthrough said closed free loop and said loop being adjacent to theemerging portion of said coil lead wire, said free ends of saidre-inforcing strand and said free end of said coil lead wire all beingmutually adjacent; and an electrical terminal member to which all ofsaid free ends are physically attached and electrically connected.

2. A re-inforced electrical coil lead according to claim 1, wherein saidre-inf-orcing strand is a multiple strand wire carrying a continuousfilm of electrical insulating material.

References Cited by the Examiner UNITED STATES PATENTS 605,930 6/08Stauffer 140-90 1,442,648 1/23 Carter 338-322 X 1,672,866 6/28 Adams.

1,764,592 6/30 Adams 140-149 1,900,585 3/33 Reed 339275 2,694,419 11/54Larsen 140149 2,760,178 8/56 Schaefer 339-275 2,829,226 4/58 Ripley.2,835,283 5/58 Thone et a1. 140-149 2,943,135 6/ Bertling 174-79 X 7FOREIGN PATENTS 584,027 1/47 Great Britain.

JOSEPH D. SEERS, Primary Examiner.

ALBERT H. KAMPE, Examiner.

1. A RE-INFORCED ELECTRICAL COIL LEAD COMPRISING A COIL LEAD WIRE OFSMALL DIAMETER AND TERMINATING IN A FREE END; A RE-INFORCING STRAND OFSUBSTANTIALLY LARGER DIAMETER THAN SAID COIL LEAD WIRE AND HAVING TWOFREE ENDS, THE CENTRAL PORTION OF SAID RE-INFORCING STRAND EXTENDING INTGE FORM OF A SMALL CLOSED FREE LOOP AND THE PORTIONS OF SAIDRE-INFORCING STRAND BETWEEN SAID LOOP AND THE FREE ENDS OF SAID STRANDBEING TWISTED TOGETHER IN THE FORM OF TWO SIDE-BY-SIDE HELICES HAVING ACOMMON CENTRAL AXIS, SAID HELICES DEFINING A CONTINUOUS HELICAL VALLEY,SAID COIL LEAD WIRE EXTENDING FROM ITS FREE END ALONG SAID CONTINUOUSHELICAL VALLEY AND BEING NESTED THEREIN, SAID COIL LEAD WIRE EMERGINGTHROUGH SAID CLOSED FREE LOOP AND SAID LOOP BEING ADJACENT TO THEEMERGING PORTION OF SAID COIL LEAD WIRE, SAID FREE ENDS OF SAIDRE-INFORCING STRAND AND SAID FREE END OF SAID COIL LEAD WIRE ALL BEINGMUTUALLY ADJACENT; AND AN ELECTRICAL TERMINAL MEMBER TO WHICH ALL OFSAID FREE ENDS ARE PHYSICALLY ATTACHED AND ELECTRICALLY CONNECTED.